/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.socket.messaging;

import java.util.ArrayList;
import java.util.List;

import org.springframework.context.ApplicationContext;
import org.springframework.core.annotation.AnnotationAwareOrderComparator;
import org.springframework.lang.Nullable;
import org.springframework.messaging.MessageChannel;
import org.springframework.messaging.SubscribableChannel;
import org.springframework.messaging.handler.MessagingAdviceBean;
import org.springframework.messaging.handler.annotation.support.AnnotationExceptionHandlerMethodResolver;
import org.springframework.messaging.simp.SimpMessageSendingOperations;
import org.springframework.messaging.simp.annotation.support.SimpAnnotationMethodMessageHandler;
import org.springframework.web.method.ControllerAdviceBean;

/**
 * A sub-class of {@link SimpAnnotationMethodMessageHandler} to provide support
 * for {@link org.springframework.web.bind.annotation.ControllerAdvice
 * ControllerAdvice} with global {@code @MessageExceptionHandler} methods.
 *
 * @author Rossen Stoyanchev
 * @since 4.2
 */
public class WebSocketAnnotationMethodMessageHandler extends SimpAnnotationMethodMessageHandler {

    public WebSocketAnnotationMethodMessageHandler(SubscribableChannel clientInChannel,
            MessageChannel clientOutChannel, SimpMessageSendingOperations brokerTemplate) {

        super(clientInChannel, clientOutChannel, brokerTemplate);
    }


    @Override
    public void afterPropertiesSet() {
        initControllerAdviceCache();
        super.afterPropertiesSet();
    }

    private void initControllerAdviceCache() {
        ApplicationContext context = getApplicationContext();
        if (context == null) {
            return;
        }
        if (logger.isDebugEnabled()) {
            logger.debug("Looking for @MessageExceptionHandler mappings: " + context);
        }
        List<ControllerAdviceBean> beans = ControllerAdviceBean.findAnnotatedBeans(context);
        AnnotationAwareOrderComparator.sort(beans);
        initMessagingAdviceCache(MessagingControllerAdviceBean.createFromList(beans));
    }

    private void initMessagingAdviceCache(@Nullable List<MessagingAdviceBean> beans) {
        if (beans == null) {
            return;
        }
        for (MessagingAdviceBean bean : beans) {
            Class<?> type = bean.getBeanType();
            if (type != null) {
                AnnotationExceptionHandlerMethodResolver resolver = new AnnotationExceptionHandlerMethodResolver(type);
                if (resolver.hasExceptionMappings()) {
                    registerExceptionHandlerAdvice(bean, resolver);
                    logger.info("Detected @MessageExceptionHandler methods in " + bean);
                }
            }
        }
    }


    /**
     * Adapt ControllerAdviceBean to MessagingAdviceBean.
     */
    private static class MessagingControllerAdviceBean implements MessagingAdviceBean {

        private final ControllerAdviceBean adviceBean;

        private MessagingControllerAdviceBean(ControllerAdviceBean adviceBean) {
            this.adviceBean = adviceBean;
        }

        public static List<MessagingAdviceBean> createFromList(List<ControllerAdviceBean> beans) {
            List<MessagingAdviceBean> result = new ArrayList<>(beans.size());
            for (ControllerAdviceBean bean : beans) {
                result.add(new MessagingControllerAdviceBean(bean));
            }
            return result;
        }

        @Override
        @Nullable
        public Class<?> getBeanType() {
            return this.adviceBean.getBeanType();
        }

        @Override
        public Object resolveBean() {
            return this.adviceBean.resolveBean();
        }

        @Override
        public boolean isApplicableToBeanType(Class<?> beanType) {
            return this.adviceBean.isApplicableToBeanType(beanType);
        }

        @Override
        public int getOrder() {
            return this.adviceBean.getOrder();
        }
    }

}
